<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
</head>
<style>
	body{
		margin: 0;
		padding: 0;
		background-color: rgba(225,225,225,1.00)
	}
	body>input{
		width: 150px;
		transition: .9s
	}
	body>input:focus{
		box-shadow: 1px 1px 15px 1px skyblue;
		width: 300px;
		
	}
	
	</style>
<body>
	这是个文本框：<input type="text">
</body>
</html>
